exoskeletoii of chitiii 

 quantities of lime. 



Fig. i. Crustacean. 



A Wood-louse. 

 Enlarged. (From U. S. 

 Dei't. A(/ric.} 



is often impregnated with large 



The Class Arachnida includes 

 the spiders, mites, ticks and scor- 

 pions. These animals breathe by 

 means of air-tubes (tracheae), or 

 air-sacs. Certain species, mitea. 

 especially, have the entire surface 

 of the body adapted for respira- 

 tion. In the case of most mem- 

 bers of this group, the head and 

 thorax are fused to form a cepha- 

 lothorax, and the eyes are simple. 



The scorpions (Fig. 2) are weU 

 known in tropical countries, on 

 account of the painful sting they 

 are able to inflict. They are 

 mostly predaceous and nocturnal 

 in habit, living in damp situations. 



Fig. 2. Arachnid. A scorpion. 

 Slifjhtly reduced. (Original.) 



The whip scorpions (Fig. 3) receive their name from the 

 long lash-like development of the first pair of legs. In the 

 illustration these are the slender appendages which are 



